Axel Vogt schrieb:> > In Maple (which - to answer your latter question - is not free of> strange behaviours):> > eval( (a+b*I)/(c-I*d), I=-I );> > a - b I> -------> c + d I> > There is a (non-recursive) command 'substitute' as well, it would do> here.> > For the other example given by Richard Fateman:> > simplify( x^2, {x^2=y^4} );> 4> y> > This is called 'simplification with side relations' (=w.r.t> equations).> > It however would not work for simplify( 1/sqrt(x^3), {sqrt(x^3)=y} ),> the command needs polynomial relations.> > And it does not work for constants like simplify( 1/sqrt(2), {2=y^2}> ).

Do I understand you correctly that it is impossible in Maple tosubstitute something for arbitrary subexpressions? Are only variables(and predefined constants like I) allowed? Would